1. Field Of The Invention
The present invention relates to seats for sealing the space between a floating roof and an inner tank wall within a storage tank for petrochemical or other liquid products.
2. History Of The Prior Art
It is standard practice in the field of large storage tanks such as oil storage tanks having floating roofs to provide the floating roof with a seal. Such seals act to seal the space between the outer rim of the floating roof and the inner tank wall, while at the same time allowing the floating roof to rise or drop as the height of the liquid product within the storage tank varies. Such seals are necessary in order to prevent harmful hydrocarbon vapors from escaping through the space between the floating roof and the inner tank wall and entering the atmosphere. Seals for floating roofs within storage tanks can assume a variety of different configurations. Examples of the different possible configurations of floating roof seals are provided by U.S. Pat. No. 4,308,968 of Thiltgen et al., U.S. Pat. No. 5,078,293 of Lippiello, U.S. Pat. No. 5,103,992 of Lippiello et al. and U.S. Pat. No. 5,301,828 of McKay. Such patents are commonly assigned with the present application. The seals depicted by these patents assume various different configurations, and typically utilize vapor barrier fabrics in conjunction with other materials. Several of the configurations utilize shoe seals which are suspended from the outer edge of the floating roof for disposition adjacent and biasing against the inner tank wall.
The floating roof seals described in the above-mentioned patents are capable of sealing the space between the floating roof and the inner tank wall effectively. However, there is a continuing need for floating roof seals that provide other options and alternatives in terms of design, fabrication and installation. Thus, while shoe type seals provide effective sealing arrangements, the apparatus required to suspend the shoes from the floating roof may be complex, expensive, or difficult to install. Seals of relatively simple design and low cost may present particular advantages for many installations.
It is therefore a desirable goal to provide improved floating roof seals that may offer certain advantages over existing seals. In particular, it would be desirable to provide seal designs which work in a very efficient and effective manner while at the same time providing certain advantages such as simplicity of design, low cost fabrication and ease of installation.